Two-Dimensional Materials-Based Josephson Junctions

TL;DR

This paper investigates the quantum transport properties of a monolayer MoS2-based Josephson junction, revealing conditions for Majorana zero modes and the behavior of Josephson current depending on the superconductor type and chemical potential.

Contribution

It introduces a tight-binding model to analyze Majorana modes and Josephson currents in 2D MoS2 junctions with topological and non-topological leads, highlighting their distinct behaviors.

Findings

Majorana zero modes form when chemical potential is much smaller than pairing potential.

Josephson current is sinusoidal with ordinary leads and zero with topological leads.

The junction acts as a two-state switch based on chemical potential, distinguishing Majorana and Andreev bound states.

Abstract

We consider a two-dimensional monolayer MoS2-based Josephson junction which is composed by an intermediate semiconductor flake and the semi-infinite topological and non-topological superconductor leads and study its quantum transport properties by using the tight-binding non-equilibrium Green function method. By introducing a simple tight-binding model, it is shown that, when the absolute value of chemical potential is much smaller than the superconductor paring potential, the Majorana zero modes, whose Chern number is two, are formed in the topological leads. Also, we show that, in Josephson junction with ordinary superconductor leads, the Josephson current has sinusoidal behavior (due to forming the Andreev bound states (ABS)), when the absolute value of energy of carriers (and the chemical potential) is much smaller (greater) than the superconductor pairing potential. Of course, for Josephson junction with topological superconductor leads, it is shown that the ABS are not formed and in consequence the related Josephson current is zero. Therefore, one can consider the two-dimensional monolayer MoS2-based Josephson junction as a two-state switch which is in open-state (due to ABS) when the chemical potential is greater than 0.8 eV and is in close-state (due to Majorana) when the chemical potential is less than < 0.8 or is equal to zero, i.e., ABS cannot mimic the Majorana state, as zero-bias conductance.